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Overcoming Spectral Inconsistency Induced Image Artifacts In Photon Counting Ct Systems
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Book Synopsis Overcoming Spectral Inconsistency-induced Image Artifacts in Photon Counting CT Systems by : Mang Feng
Download or read book Overcoming Spectral Inconsistency-induced Image Artifacts in Photon Counting CT Systems written by Mang Feng and published by . This book was released on 2021 with total page 131 pages. Available in PDF, EPUB and Kindle. Book excerpt: Photon counting detectors (PCDs) use semiconductors such as silicon (Si) or cadmium telluride (CdTe) to directly convert the energy of X-rays to electric (i.e. voltage) pulse signals. The seminconductor sensor and readout electronics of PCDs are fast enough such that the pulses induced by individual X-ray photons can be discriminated and recorded as separate digital counts. Compared with conventional scintillator-based indirect-conversion detectors, the direct conversion mechanism of PCDs can effectively improve spatial resolution. PCDs are equipped with voltage comparators to effectively reject electronic noise and improve images' contrast-to-noise ratio, particularly at low radiation dose levels. By introducing multiple comparators to each detector pixel, the energy of each X-ray photon can be estimated based on the height of the voltage pulse. These attractive features of PCDs offer the potential of further reducing radiation dose and achieving routine spectral imaging in x-ray computed tomography (CT). However, there is a technical challenge in the way of using PCD in clinical CT: the energy response functions of PCDs are inconsistency across different semiconductor panels due to slight variations in the semiconductor impurity level, threshold voltage, and other physical reasons. This spectral inconsistency problem leads to concentric artifacts in reconstructed PCD-CT images that severely degrade low-contrast detectability and material quantification accuracy. This thesis presents two methods to address the spectral inconsistency-induced concentric artifacts in PCD-CT: The first method method leverages the energy-resolving capability of PCDs to perform project-domain material decomposition to decouple the image object's information from the detector response function. The second method does not require a PCD to be operated under the spectral imaging mode; instead, it uses an image-domain segmentation process to help estimating the non-water contents in an image object, based on which detector pixel-specific correction functions were applied to address the nonuniformity in the raw projection data. Both methods were experimentally evaluated on a benchtop PCD-CT system and a prototype C-arm PCD-CT system with human-sized phantoms, human cadavers, and in vivo large animals. The experimental results demonstrated that the spectral inconsistency-induced artifacts in PCD-CT can be effectively addressed with the proposed methods. Finally, this thesis demonstrates examples of how the correction methods can be employed to accomplish high-quality and quantitative virtual non-contrast imaging, virtual monoenergetic imaging, and dual K-edge contrast material PCD-CT imaging.
Book Synopsis Spectral, Photon Counting Computed Tomography by : Katsuyuki Taguchi
Download or read book Spectral, Photon Counting Computed Tomography written by Katsuyuki Taguchi and published by CRC Press. This book was released on 2020-07-14 with total page 446 pages. Available in PDF, EPUB and Kindle. Book excerpt: Spectral, Photon Counting Computed Tomography is a comprehensive cover of the latest developments in the most prevalent imaging modality (x-ray computed tomography (CT)) in its latest incarnation: Spectral, Dual-Energy, and Photon Counting CT. Disadvantages of the conventional single-energy technique used by CT technology are that different materials cannot be distinguished and that the noise is larger. To address these problems, a novel spectral CT concept has been proposed. Spectral Dual-Energy CT (DE-CT) acquires two sets of spectral data, and Spectral Photon Counting CT (PC-CT) detects energy of x-ray photons to reveal additional material information of objects by using novel energy-sensitive, photon-counting detectors. The K-edge imaging may be a gateway for functional or molecular CT. The book covers detectors and electronics, image reconstruction methods, image quality assessments, a simulation tool, nanoparticle contrast agents, and clinical applications for spectral CT.
Download or read book Spectral Imaging written by Hatem Alkadhi and published by Springer Nature. This book was released on 2022-05-02 with total page 375 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book, edited by leading experts in radiology, offers a state-of-the-art overview of the specifics and the added value of dual-energy, multi-energy, and spectral computed tomography (CT). Latest advances and upcoming innovations such as photon-counting detector CT are covered by renown experts in the field. The entire spectrum of clinical applications of dual-energy and spectral CT throughout the body is covered. Book chapters are written by expert authors with a background in physics and radiology and are richly illustrated with high quality figures, graphical illustrations, and tables. The first section covers background issues and the most relevant technical aspects of the technique, including a detailed description of the approaches to dual-energy, spectral and photon-counting CT by different vendors of CT scanners. The second part focusses on the use of dual-energy, spectral and photon-counting CT in daily clinical practice, and individual chapters are devoted to imaging of the brain, cardiovascular system, gastrointestinal tract, abdominal organs, skeletal system, and the chest. The focus of the book ensures that it will be of interest for a multidisciplinary forum of readers comprising radiologists, medical physicists, and other medical professionals and scientists being interested in cutting-edge CT imaging.
Book Synopsis Photon Counting Computed Tomography by : Scott Hsieh
Download or read book Photon Counting Computed Tomography written by Scott Hsieh and published by Springer Nature. This book was released on 2023-05-27 with total page 271 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book will provide readers with a good overview of some of most recent advances in the field of Photon Counting CT technology for X-ray medical imaging, especially as it pertains to new detectors. There will be a good mixture of general chapters in both technology and applications in CT medical imaging. The book will have an in-depth review of the research topics from world-leading specialists in the field. The conversion of the X-ray signal into analogue/digital value will be covered in some chapters. The authors also provide a review of CMOS chips for X-ray image sensors, methods of material discrimination and image reconstruction techniques. Covers a broad range of topics, including an introduction to novel spectral Computed Tomography; Includes in-depth analysis on how to optimize X-ray detection; Discusses analysis of electronics for X-ray detection.
Book Synopsis Multi-energy Image Reconstruction in Spectral Photon-counting CT by : Pei Niu
Download or read book Multi-energy Image Reconstruction in Spectral Photon-counting CT written by Pei Niu and published by . This book was released on 2020 with total page 109 pages. Available in PDF, EPUB and Kindle. Book excerpt: Spectral photon-counting CT (sCT) appeared recently as a new imaging technique presenting fundamental advantages with respect to conventional CT and duel-energy CT. However, due to the reduced number of photons in each energy bin of sCT and various artifacts, image reconstruction becomes particularly difficult. This thesis focuses on the reconstruction of multi-energy images in sCT. First, we propose to consider the ability of sCT to achieve simultaneously both anatomical (aCT) and functional imaging (fCT) in one single acquisition through reconstruction and material decomposition. aCT function of sCT is studied under the same configuration as that of conventional CT, and fCT function of sCT is investigated by applying material decomposition algorithms to the same acquired multi-energy data. Then, since noise is a particularly acute problem due to the largely reduced number of photons in each energy bin of sCT, we introduce denoising mechanism in the image reconstruction to perform simultaneous reconstruction and denoising. Finally, to improve image reconstruction, we propose to reconstruct the image at a given energy bin by exploiting information in all other energy bins. The key strategy in such approach consists of grouping the similar pixels from the reconstruction of all the energy bins into the same class, fitting within each class, mapping the fitting results into each energy bin, and denoising with the mapped information. It is used both as a post-denoising operation to demonstrate its effectiveness and as a regularization term or a combined regularization term for simultaneous reconstruction and denoising. All the above methods are evaluated on both simulation and real data from a pre-clinical sCT system.
Book Synopsis Application of Photon Counting Detectors to X-ray CT Systems by : Xu Ji
Download or read book Application of Photon Counting Detectors to X-ray CT Systems written by Xu Ji and published by . This book was released on 2020 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recently, photon counting detectors (PCDs) have attracted a lot of research interest for applications in x-ray imaging. This type of detector utilizes a detection mechanism which counts each individual photon and offers several attractive features, including low dark current signal, high spatial resolution, high detective quantum efficiency and energy resolving capability. Therefore, PCDs have the potential to improve the current computed tomography (CT) technology in the field of low dose CT and spectral CT imaging. However, some technical challenges remain in PCD technology, e.g., loss of counts under a high flux x-ray beam and spectral distortion due to shared charges between pixels. Meanwhile, the detection mechanism of PCDs brings about additional detector settings, e.g., detector thresholds and operational modes. The optimization of the selection of PCD settings for a specific imaging task may become an issue for the users. In this dissertation, the research focus is on the incorporation of a PCD into an x-ray CT system for a specific clinical or research purpose. The major objectives of the dissertation are (i) to perform a theoretical analysis to model the behavior of PCDs under different detector settings and incoming x-ray spectra; (ii) to develop a framework to optimize the detector settings for a given imaging task; and (iii) to utilize the energy resolving capability of the PCDs for three-material decomposition. There are three major outcomes corresponding to the three objectives. (i) A cascaded system analysis was performed which incorporated the anti-charge sharing function of the PCDs. The cascaded model is capable of predicting the multiplicity, zero-frequency detective quantum efficiency and energy response function of a CdTe-based PCD. (ii) A benchtop PCD-based CT system was optimized for the intracranial hemorrhage evaluation tasks. The optimized CT images from the PCD-based CT system demonstrated advantages over those from a commercial diagnostic CT system. (iii) The PCD operated under spectral mode was innovatively combined with the x-ray differential phase contrast imaging technique to enable a three-material decomposition task. The decomposition results demonstrated potential advantages over those using the three energy bins from a PCD. The methods and results in this dissertation should facilitate the applications of PCDs to modern x-ray CT systems in the future.
Book Synopsis Spectral Multi-Detector Computed Tomography (sMDCT) by : Xiangyang Tang
Download or read book Spectral Multi-Detector Computed Tomography (sMDCT) written by Xiangyang Tang and published by CRC Press. This book was released on 2023-12-11 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt: X-ray computed tomography (CT) has been one of the most popular diagnostic imaging modalities for decades in the clinic for saving patients’ lives or improving their quality of life. This book is an introductory one-stop shop for technological and clinical topics in multi-detector computed tomography (MDCT). Starting with MDCT’s fundamentals in physics and mathematics, the book provides an in-depth introduction to its system architecture and imaging chain, signal detection via energy-integration and photon-counting mechanisms, clinical application-driven scan modes and protocols, analytic and iterative image reconstruction solutions, and spectral imaging – the latest technological advancement in MDCT. The book extends its coverage on image quality assessment under the theory of signal detection and statistical decision. In recognition of its clinical relevance for conspicuity enhancement in angiographic and parenchymal imaging applications, the book features a chapter dedicated to the fundamental (chemical, physical and physicochemical) properties and clinical administration of iodinated contrast agent. The book ends with an outlook of the contrast agents that are novel in material and delivery, and their synergy with spectral MDCT to elevate CT’s contrast resolution in cardiovascular, neurovascular and oncologic applications. This book will be an invaluable reference for researchers, engineers, radiological physicians and technologists, and graduate and senior undergraduate students. Features Provides an accessible introduction to the subject Up to date with the latest advances in emerging technologies and procedures Provides a historical overview of CT technology Xiangyang Tang, PhD, is an imaging scientist with extensive research and development experience in industry (GE Healthcare), academia (Emory University School of Medicine) and the clinic (Emory Healthcare). With a focus on computed tomography, Tang has been working in the field of medical imaging for more than 20 years. He is a professor of radiology and imaging sciences at Emory University School of Medicine, Fellow of SPIE (International Society for Optics and Photonics) and Fellow of AAPM (American Association of Physicists in Medicine). Along with the publication of more than 200 papers in leading scientific journals and conferences, his contributions to the scientific community include serving as associate editor for a number of prestigious journals, in addition to working on the scientific committees of leading conferences and panels for numerous federal and foundational study sections.
Book Synopsis Optimization in Spectral X-ray/CT Imaging Measurements by : Yuan Yao
Download or read book Optimization in Spectral X-ray/CT Imaging Measurements written by Yuan Yao and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Spectral imaging techniques can enhance clinical x-ray/CT applications by creating material discriminated images and facilitating quantitative analysis based on intrinsic tissue properties. This dissertation focused on improving the performance of spectral x-ray/CT imaging by optimizing system designs and scan protocols. I designed and demonstrated that a fixed K-edge x-ray filter can improve material decomposition precision of fast kVp-switching systems at modest flux penalty. Secondly, I optimized the protocols of dual source liver CT, where I showed that the dual energy blended images would not have as good contrast to noise ratio (CNR) as optimized single energy scans. Besides commercially available x-ray/CT systems, photon counting x-ray detectors (PCXD) are promising for spectral imaging applications, but for medical use they suffer from non-ideal energy response and slow counting speed. Edge-on PCXD with multi-layer segmentation was proposed to address the counting speed issue by splitting the counting burden into multiple layers. We hypothesized that segmenting detectors in the depth direction (a.k.a. "in-depth") and retaining the depth dependent signals can also significantly improve the spectral performance (e.g., noise of material discriminated images). Our research showed that the depth information is redundant when the pulse height information is perfect. With real-world, non-ideal energy response functions (ERF), however, the in-depth PCXD is more dose efficient than the edge-on PCXD. Firstly, when analytical ERF models were assumed, we found the benefit of the depth information varied across different detector materials but was relatively constant across various detector architectures, protocol settings, and the scanned object size. The dose efficiency improvement comes along with the fact that the depth information helps when photons that are recorded at wrong energies overlap with correctly measured ones. Next, we compared the in-depth and edge-on detectors using more realistic ERFs estimated from Monte Carlo simulation, which showed that the depth segmentation degrades the energy response by introducing inter-layer cross-talk. The results showed that severe data correlation between layers diminish the benefit from the depth segments, but with correction schemes applied, the dose improvement reappears. The improvements are ERF dependent, with high potential when ERF degradation is from K-escape photons and little impact for events in the Compton plateau.
Author :Björn J. Heismann Publisher :SPIE-International Society for Optical Engineering ISBN 13 :9780819492579 Total Pages :0 pages Book Rating :4.4/5 (925 download)
Book Synopsis Spectral Computed Tomography by : Björn J. Heismann
Download or read book Spectral Computed Tomography written by Björn J. Heismann and published by SPIE-International Society for Optical Engineering. This book was released on 2012 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Computed tomography (CT) is a widely used x-ray scanning technique. In its prominent use as a medical imaging device, CT serves as a workhorse in many clinical settings throughout the world. It provides answers to urgent diagnostic tasks such as oncology tumor staging, acute stroke analysis, or radiation therapy planning. Spectral Computed Tomography provides a concise, practical coverage of this important medical tool. The first chapter considers the main clinical motivations for spectral CT applications. In Chapter 2, the measurement properties of spectral CT systems are described. Chapter 3 provides an overview of the current state of research on spectral CT algorithms. Based on this overview, the technical realization of spectral CT systems is evaluated in Chapter 4. Device approaches such as DSCT, kV switching, and energy-resolving detectors are compared. Finally, Chapter 5 summarizes various algorithms for spectral CT reconstructions and spectral CT image postprocessing, and links these algorithms to clinical use cases
Book Synopsis Multi-dimensional Extension of the Alternating Minimization Algorithm in X-ray Computed Tomography by : Jingwei Lu
Download or read book Multi-dimensional Extension of the Alternating Minimization Algorithm in X-ray Computed Tomography written by Jingwei Lu and published by . This book was released on 2019 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt: X-ray computed tomography (CT) is an important and effective tool in medical and industrialimaging applications. The state-of-the-art methods to reconstruct CT images have hadgreat development but also face challenges. This dissertation derives novel algorithms toreduce bias and metal artifacts in a wide variety of imaging modalities and increase performancein low-dose scenarios.The most widely available CT systems still use the single-energy CT (SECT), which isgood at showing the anatomic structure of the patient body. However, in SECT imagereconstruction, energy-related information is lost. In applications like radiation treatmentplanning and dose prediction, accurate energy-related information is needed. Spectral CThas shown the potential to extract energy-related information.Dual-energy CT (DECT) is the first successful implementation of spectral CT. By using twodifferent spectra, the energy-related information can be exported by reconstructing basis-materialimages. A sinogram-based decomposition method has shown good performance inclinical applications. However, when the x-ray dose level is low, the sinogram-based decompositionmethods generate biased estimates. The bias increases rapidly when the dose leveldecreases. The bias comes from the ill-posed statistical model in the sinogram-decompositionmethod. To eliminate the bias in low-dose cases, a joint statistical image reconstruction(JSIR) method using the dual-energy alternating minimization (DEAM) algorithm is proposed.By correcting the ill-posed statistical model, a relative error as high as 15% in thesinogram-based decomposition method can be reduced to less than 1% with DEAM, whichis an approximately unbiased estimation.Photon counting CT (PCCT) is an emerging CT technique that also can resolve the energyinformation. By using photon-counting detectors (PCD), PCCT keeps track of the energyof every photon received. Though PCDs have an entirely different physical performancefrom the energy-integrating detectors used in DECT, the problem of biased estimation withthe sinogram-decomposition method remains. Based on DEAM, a multi-energy alternatingminimization (MEAM) algorithm for PCCT is proposed. In the simulation experiments,MEAM can effectively reduce bias by more than 90%.Metal artifacts have been a concern since x-ray CT came into medical imaging. When thereexist dense or metal materials in the scanned object, the image quality may suffer severeartifacts. The auxiliary sinogram alternating minimization (ASAM) algorithm is proposedto take advantages of two major categories of methods to deal with metal artifacts: thepre-processing method and statistical image reconstruction. With a phantom experiment, ithas been shown that ASAM has better metal-artifact reduction performance compared withthe current methods.A significant challenge in security imaging is that due to the large geometry and powerconsumption, low photon statistics are detected. The detected photons suffer high noise andheavy artifacts. Image-domain regularized iterative reconstruction algorithms can reducethe noise but also result in biased reconstruction. A wavelet-domain penalty is introducedwhich does not bring in bias and can effectively eliminate steaking artifacts. By combiningthe image-domain and wavelet-domain penalty, the image quality can be further improved.When the wavelet penalty is used, a concern is that no empirical way, like in the image-domainpenalty, is available to determine the penalty weight. Laplace variational automaticrelevance determination (Lap-VARD) method is proposed to reconstruct the image andoptimal penalty weight choice at the same time.
Book Synopsis Image-domain Material Decomposition in Spectral Photon-counting CT for Medical Applications by : Bingqing Xie
Download or read book Image-domain Material Decomposition in Spectral Photon-counting CT for Medical Applications written by Bingqing Xie and published by . This book was released on 2020 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: Material decomposition is a fundamental and primordial problem in spectral photon-counting X-ray CT (sCT). The present thesis focuses on the development of material decomposition methods using spectral and morphological information embedded in multi-energy sCT images. In this framework, three methods were developed. For the first method, by using bounded mass density, local joint sparsity and structural low-rank (DSR) in image domain, we achieve highly accurate decomposition of materials such as gadolinium, iodine and iron. The results on both numerical phantom and physical data demonstrated that the proposed DSR method leads to more accurate decomposition than usual pseudo-inverse method with singular value decomposition (SVD) and current popular sparse regularization method with L1-norm constraint. The second method works in a region-wise manner. It consists in optimizing basis materials based on spatio-energy segmentation of regions-of-interests (ROIs) in sCT images, reducing noise by averaging multi-energy spatial images, and performing a fine material decomposition involving optimized decomposition matrix, denoising regularization and sparsity regularization. The results on both digital and physical data showed that the proposed ROI-wise material decomposition method presents clearly higher reliability and accuracy compared to common decomposition methods based on total variation (TV) or L1-norm (lasso) regularization. In the third method, we propose the notion of super-energy-resolution (SER) sCT imaging, which is realized through establishing the relationship between simulation and physical phantoms by means of coupled dictionary learning in a pixel-wise way. The effectiveness of the proposed methods was validated on digital phantom, physical phantoms and in vivo data. The results showed that for the same decomposition method using lasso regularization, the proposed super-energy-resolution imaging presents much higher decomposition accuracy and detection ability compared to what can be provided by current sCT machine.
Book Synopsis System-wide Advances in Photon-counting CT : Corrections, Simulations, and Image Analysis by : Matthew Getzin
Download or read book System-wide Advances in Photon-counting CT : Corrections, Simulations, and Image Analysis written by Matthew Getzin and published by . This book was released on 2019 with total page 348 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Scatter Correction for Spectral Computed Tomography by : Odran Pivot
Download or read book Scatter Correction for Spectral Computed Tomography written by Odran Pivot and published by . This book was released on 2019 with total page 113 pages. Available in PDF, EPUB and Kindle. Book excerpt: Scattered radiation is a major cause of bias, loss of contrast and artifacts in x-ray computed tomography (CT). Many correction methods have been proposed for conventional CT (using energy-integrating detectors) but it is still an open research topic in the field of spectral CT, a novel imaging technique based on the use of energy-selective photon counting detectors. The main objective of the present thesis was to investigate scatter correction techniques adapted to spectral CT. The chosen solution refines a scatter correction method developed for integration-mode CT which uses a semi-transparent primary modulator mask. The attenuation of the primary modulator mask is first compensated for with a correction matrix which takes advantage of the spectral information. The other contributions are a scatter model based on B-splines allowing an accurate representation of scatter maps with the aid of a very few parameters and a cost function which takes into account the structures of the mask and the object. The accuracy of the correction matrix, the scatter model and the whole proposed scatter correction process were tested on simulated data considering photon counting detectors with various numbers of energy bins and have shown a significant bias reduction, contrast enhancement and artifact removal. In addition, physical experiments were performed using a parallel fan-beam set-up with a commercial energy-resolved detector. The method was successfully validated in the case of two phantoms dedicated to medical image quality measurements, with a remarkable improvement.
Book Synopsis Characterization and Correction of Spectral CT Image Artifacts by : Fredericke Schmidt
Download or read book Characterization and Correction of Spectral CT Image Artifacts written by Fredericke Schmidt and published by . This book was released on 2010 with total page 63 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Medical Imaging Systems by : Andreas Maier
Download or read book Medical Imaging Systems written by Andreas Maier and published by Springer. This book was released on 2018-08-02 with total page 263 pages. Available in PDF, EPUB and Kindle. Book excerpt: This open access book gives a complete and comprehensive introduction to the fields of medical imaging systems, as designed for a broad range of applications. The authors of the book first explain the foundations of system theory and image processing, before highlighting several modalities in a dedicated chapter. The initial focus is on modalities that are closely related to traditional camera systems such as endoscopy and microscopy. This is followed by more complex image formation processes: magnetic resonance imaging, X-ray projection imaging, computed tomography, X-ray phase-contrast imaging, nuclear imaging, ultrasound, and optical coherence tomography.
Book Synopsis Spectral Computed Tomography with a Photon-Counting Silicon-Strip Detector by : Mats Persson
Download or read book Spectral Computed Tomography with a Photon-Counting Silicon-Strip Detector written by Mats Persson and published by . This book was released on 2016 with total page 43 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Spectral Photon-Counting Computed Tomography with Silicon Detectors: New Models and Applications by : Fredrik Grönberg
Download or read book Spectral Photon-Counting Computed Tomography with Silicon Detectors: New Models and Applications written by Fredrik Grönberg and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
